Carbon nanotubes (CNTs) have been envisioned as one of the most promising engineering materials due to its excellent thermal, mechanical and electrical properties. The application of carbon nanotubes can be found in a variety of areas such as energy, MEMS and electronics. There are in principle three mature CNT fabrication technologies, arc discharge, laser ablation and chemical vapor deposition. Among all these three production methods, thermal chemical vapor deposition (CVD) has the advantage of flexible patterning and growing vertically aligned CNTs, which is enabled by photolithographically defining the growth catalyst metals.
The use and development of carbon nanotubes has expanded, as these materials have shown to be valuable in next generation industries including the fields of electronics and chemistry. Further development of carbon nanotube technology allows organized structures or intertwined randomly oriented bundles of carbon nanotubes to be formed. Techniques have been developed to controllably build organized architectures of nanotubes having predetermined orientations, such as vertically aligned nanotubes. Although such structures may be useful for a variety of purposes, the structures by themselves may be limited in terms of function and application.
In the area of flexible electronics for example, printed, sputtered or evaporated metal wires are the most common material used in making the electrical interconnects in the flexible electronics. However, traditional laser or etching technologies cannot be applied to flexible materials, such as PET, PEN or silicone based polymeric materials. This limitation greatly cripples the manufacturability to make vertical direct electrical interconnects in flexible substrates. Unlike metals, vertically aligned CNT bundles can be synthesized without any supporting or sacrificial layers. The CVD-grown CNTs are attached to the growing substrate by weak Van der Waals force and can therefore be easily manipulated by various methods such a coating, doping, densification or transfer. This merit makes the CNTs suitable for use in polymer based composite materials which require mechanical flexibility together with the electrical conductivity. Blending of CNTs into polymers has been extensively studied in recent years, and the application of such CNT-polymer composites can be found in a lot of areas such as biology, medicine, electronics and functional membranes/surface.